Regensburg 2010 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 6: Magnetic Thin Films I (Heusler Alloys)

MA 6.8: Vortrag

Montag, 22. März 2010, 16:15–16:30, H10

Fe-rich Heusler/semiconductor hybrid structures: An ab initio study of the electronic and magnetic structure of the interface — •Heike C. Herper and Peter Entel — Faculty of Physics, University of Duisburg-Essen, 47048 Duisburg, Germany

Ferromagnet(FM)-semiconductor(SC) hybrid structures have attracted much interest concerning the fabrication of spintronic devices. Fe and Co based Heusler alloys seem to be suitable for this purpose, because they are often half-metallic or have at least a high spin-polarization and a high T_C. Though, some of the stoichiometric systems have been intensively studied only few results exist for the nonstoichiometric systems and for the magnetic structure of the FM/SC interface. We focus on Fe₂Fe_1−xY_xSi (Y = Co, Ni) Heusler alloys. Fe₃Si and Fe₂CoSi are known to have high T_Cs and being close to half-metallicity. In agreement with experiment we observe that the replacement of Fe by Co or Ni leads to an inverse Heusler ordering instead of the L2₁ structure. However, it turns out that the magnetic properties are sensitive to strain which may occur at interfaces.

First, we investigate the dependence on the concentration x and the structural ordering for the bulk phases. In a second step we perform calculations for the Fe-rich Heuslers on GaAs(001) and MgO(001) to study the polarization, the band gap etc. We observe that the polarization not only increases but also layer dependent oscillations of the polarization are reduced if Co is added to the system. The calculations are performed by using the VASP [Mater. Sci.6,15 (1996)] and SPR-KKR [by H. Ebert et al.] code.